I think the skill is computer doable and the actual app is phone based only. look it up in the Alexa info on your computer or phone and set it up. Lots and lots of strategies to get what you want done, and so much of it is free like an eagle. A feature i was surprised wasnt standard. and I really only use one as my wife likes to go to sleep with a colored light on and I can't deal with it if I wake up in the middle of the night, so I have a timer set to turn it off after she is asleep (which doesn't take but about half an hour). Another way to access the sleep option is within the fire tv settings.

I don't use any timers to turn anything but lights right now, so mine are all done through the Philips hUE app. Once you have that, you can go into the hub settings and set up an activity and with YONOMI can set up routines based on TIME. it appears all of it is done by the Alexa and the Hub. Funny thing is, if you use it, you won't even know it's there.

Called YONOMI to make things work the most seamlessly.

Sleep timer amazon fire stick